Additives and lubricant formulations for improved phosphorus retention properties

ABSTRACT

A method and compositions for lubricating surfaces with lubricating oils exhibiting increased phosphorous retention. The lubricated surface includes a lubricant composition containing a base oil of lubricating viscosity, an amount of a phosphorus-containing compound and an amount of at least one hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.

TECHNICAL FIELD

The embodiments described herein relate to particular oil soluble metal additives and use of such metal additives in lubricating oil formulations, and in particular to soluble titanium additives used to improve phosphorus retention properties of lubricant formulations that may be effective to reduce exhaust catalyst deactivation.

BACKGROUND AND SUMMARY

For over fifty (50) years automotive engine oils have been formulated with zinc dialkyl dithiophosphate (ZDDP) resulting in low levels of wear, oxidation, and corrosion. The additive is truly ubiquitous and found in nearly every modern engine oil. ZDDP imparts multifunctional performance in the areas of anti-wear, anti-oxidation, and anti-corrosion and is undeniably one of the most cost-effective additives in general use by engine oil manufacturers and marketers.

However, there is concern that phosphorus from engine oils may volatilize and pass through the combustion chamber so that elemental phosphorus is deposited on catalytic systems resulting in a loss of catalyst efficiency. ZDDP is known to provide a source of phosphorus that may cause significant problems with exhaust catalytic converters and oxygen sensors when the phosphorus from combusted oil forms an impermeable glaze that may mask precious metal catalytic sites. As a result there is pressure by the automakers to control and/or reduce the amount of phosphorus-containing compounds used in engine oils to facilitate longer converter and oxygen sensor life, and to reduce the manufacturer's initial costs of converters through lower precious metal content.

While a reduction in the phosphorus content of the lubricating oils may improve catalytic converter life or efficiency, the benefits of phosphorus additives for friction control and wear protection may not be conveniently matched by non-phosphorus containing additives. Accordingly, there is a competing need for additives and methods that enable protection of catalytic activity without significantly reducing a total phosphorus content of the lubricating oil compositions.

In one embodiment herein is presented a lubricated surface containing a lubricant composition including a base oil of lubricating viscosity, an amount of a phosphorus-containing compound, and an amount of at least one hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.

In another embodiment, there is provided a vehicle having moving parts and containing a lubricant for lubricating the moving parts. The lubricant includes an oil of lubricating viscosity, at least one phosphorus-containing compound, and an amount of at least one hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.

In yet another embodiment there is provided a fully formulated lubricant composition including a base oil component of lubricating viscosity, at least one phosphorus-containing compound, and an amount of hydrocarbon soluble titanium-containing agent effective to provide a an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound, wherein the titanium-containing agent is essentially devoid of sulfur and phosphorus atoms.

A further embodiment of the disclosure provides a method of increasing phosphorus retention in engine lubricant compositions during operation of an engine, wherein the phosphorus retention is sufficient to reduce catalyst poisoning. The method includes contacting the engine parts with a lubricant composition containing a base oil of lubricating viscosity, at least one phosphorus-containing compound, and an amount of a hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.

As set forth briefly above, embodiments of the disclosure provide a hydrocarbon soluble titanium additive that may significantly improve phosphorus retention in a lubricating oil thereby reducing catalyst poisoning effects of phosphorus on catalytic converters. The additive may be mixed with an oleaginous fluid that is applied to a surface between moving parts. In other applications, the additive may be provided in a fully formulated lubricant composition. The additive is particularly directed to meeting the currently proposed GF-5 standards for passenger car motor oils and PC-10 standards for heavy duty diesel engine oil as well as future passenger car and diesel engine oil specifications. The additive may be particularly useful to enable vehicles to meet the stringent Tier-II, BIN2 120,000 mile catalyst efficiency standard.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the embodiments disclosed and claimed.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A primary component of the additives and concentrates provided for lubricant compositions described herein is a hydrocarbon soluble titanium compound. The term “hydrocarbon soluble” means that the compound is substantially suspended or dissolved in a hydrocarbon material, as by reaction or complexation of a reactive metal compound with a hydrocarbon material. As used herein, “hydrocarbon” means any of a vast number of compounds containing carbon, hydrogen, and/or oxygen in various combinations.

The term “hydrocarbyl” refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

-   -   (1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or         alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)         substituents, and aromatic-, aliphatic-, and         alicyclic-substituted aromatic substituents, as well as cyclic         substituents wherein the ring is completed through another         portion of the molecule (e.g., two substituents together form an         alicyclic radical);     -   (2) substituted hydrocarbon substituents, that is, substituents         containing non-hydrocarbon groups which, in the context of the         description herein, do not alter the predominantly hydrocarbon         substituent (e.g., halo (especially chloro and fluoro), hydroxy,         alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);     -   (3) hetero-substituents, that is, substituents which, while         having a predominantly hydrocarbon character, in the context of         this description, contain other than carbon in a ring or chain         otherwise composed of carbon atoms. Hetero-atoms include sulfur,         oxygen, nitrogen, and encompass substituents such as pyridyl,         furyl, thienyl and imidazolyl. In general, no more than two,         preferably no more than one, non-hydrocarbon substituent will be         present for every ten carbon atoms in the hydrocarbyl group;         typically, there will be no non-hydrocarbon substituents in the         hydrocarbyl group.

The hydrocarbon soluble titanium compounds suitable for use as a herein, for example as phosphorus retention agents are provided by a reaction product of a titanium alkoxide and an about C₆ to about C₂₅ carboxylic acid. The reaction product may be represented by the following formula:

wherein n is an integer selected from 2, 3 and 4, and R is a hydrocarbyl group containing from about 5 to about 24 carbon atoms, or by the formula:

wherein each of R¹, R², R³, and R⁴ are the same or different and are selected from a hydrocarbyl group containing from about 5 to about 25 carbon atoms. Compounds of the foregoing formulas are essentially devoid of phosphorous and sulfur.

In an embodiment, the hydrocarbon soluble titanium compound may be substantially or essentially devoid or free of sulfur and phosphorus atoms such that a lubricant or formulated lubricant package comprising the hydrocarbon soluble titanium compound contains about 0.7 wt % or less sulfur and about 0.12 wt % or less phosphorus.

In another embodiment, the hydrocarbon soluble titanium compound may be substantially free of active sulfur. “Active” sulfur is sulfur which is not fully oxidized. Active sulfur further oxidizes and becomes more acidic in the oil upon use.

In yet another embodiment, the hydrocarbon soluble titanium compound may be substantially free of all sulfur. In a further embodiment, the hydrocarbon soluble titanium compound may be substantially free of all phosphorus.

In a still further embodiment, the hydrocarbon soluble titanium compound may be substantially free of all sulfur and phosphorus. For example, the base oil in which the titanium compound may be dissolved in may contain relatively small amounts of sulfur, such as in one embodiment, less than about 0.5 wt % and in another embodiment, about 0.03 wt % or less sulfur (e.g., for Group II base oils), and in a still further embodiment, the amount of sulfur and/or phosphorus may be limited in the base oil to an amount which permits the finished oil to meet the appropriate motor oil sulfur and/or phosphorus specifications in effect at a given time.

Examples of titanium/carboxylic acid products include, but are not limited to, titanium reaction products with acids selected from the group consisting essentially of caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, oleic acid, erucic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, neodecanoic acid, and the like. Methods for making such titanium/carboxylic acid products are described, for example, in U.S. Pat. No. 5,260,466, the disclosure of which is incorporated herein by reference.

The hydrocarbon soluble titanium compounds of the embodiments described herein are advantageously incorporated into lubricating compositions. Accordingly, the hydrocarbon soluble titanium compounds may be added directly to the lubricating oil composition. In one embodiment, however, hydrocarbon soluble titanium compounds are diluted with a substantially inert, normally liquid organic diluent such as mineral oil, synthetic oil (e.g., ester of dicarboxylic acid), naptha, alkylated (e.g., C₁₀-C₁₃ alkyl) benzene, toluene or xylene to form a titanium additive concentrate. The titanium additive concentrates usually contain from about 0% to about 99% by weight diluent oil.

In the preparation of lubricating oil formulations it is common practice to introduce the titanium additive concentrates in the form of 1 to 99 wt. % active ingredient concentrates in hydrocarbon oil, e.g. mineral lubricating oil, or other suitable solvent. Usually these concentrates may be added to a lubricating oil with a dispersant/inhibitor (DI) additive package and viscosity index (VI) improvers containing 0.01 to 50 parts by weight of lubricating oil per part by weight of the DI package to form finished lubricants, e.g. crankcase motor oils. Suitable DI packages are described for example in U.S. Pat. Nos. 5,204,012 and 6,034,040 for example. Among the types of additives included in the DI additive package are detergents, dispersants, antiwear agents, friction modifiers, seal swell agents, antioxidants, foam inhibitors, lubricity agents, rust inhibitors, corrosion inhibitors, demulsifiers, viscosity index improvers, and the like. Several of these components are well known to those skilled in the art and are preferably used in conventional amounts with the additives and compositions described herein.

In another embodiment, the titanium additive concentrates may be top treated into a fully formulated motor oil or finished lubricant. The purpose of titanium additive concentrates and DI package, of course, is to make the handling of the various materials less difficult and awkward as well as to facilitate solution or dispersion in the final blend. A representative DI package may contain, dispersants, antioxidants, detergents, antiwear agents, antifoam agents, pour point depressants, and optionally VI improvers and seal swell agents.

Embodiments described herein provide lubricating oils and lubricant formulations in which the concentration of the hydrocarbon soluble titanium compound is relatively low, providing from about 1 to about 1500 parts per million (ppm) titanium in terms of elemental titanium in the finished lubricant composition. In one embodiment, the titanium compound is present in the lubricating oil compositions in an amount sufficient to provide from about 50 to about 1000 ppm titanium and in a further embodiment from about 50 to about 500 ppm titanium.

Lubricant compositions made with the hydrocarbon soluble titanium, additives described above are used in a wide variety of applications. For compression ignition engines and spark ignition engines, it is preferred that the lubricant compositions meet or exceed published GF-4 or API-C₁₋₄ standards. Lubricant compositions according to the foregoing GF-4 or API-C₁₋₄ standards include a base oil, the DI additive package, and/or a VI improver to provide a fully formulated lubricant. The base oil for lubricants according to the disclosure is an oil of lubricating viscosity selected from natural lubricating oils, synthetic lubricating oils and mixtures thereof. Such base oils include those conventionally employed as crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, such as automobile and truck engines, marine and railroad diesel engines, and the like.

Phosphorus-Containing Compounds

Another component of the lubricant composition is a phosphorus-containing compound such as ZDDP. Suitable ZDDPs may be prepared from specific amounts of primary and secondary alcohols. For example, the alcohols may be combined in a ratio of from about 100:0 to about 0:100 primary-to-secondary alcohols. As an even further example, the alcohols may be combined in a ratio of about 60:40 primary-to-secondary alcohols. An example of a suitable ZDDP may comprise the reaction product obtained by combining: (i) about 50 to about 100 mol % of about C₁ to about C₁₈ primary alcohol; (ii) up to about 50 mol % of about C₃ to C₁₈ secondary alcohol; (iii) a phosphorus-containing component; and (iv) a zinc-containing component. As a further example, the primary alcohol may be a mixture of from about C₁ to about C₁₈ alcohols. As an even further example, the primary alcohol may be a mixture of a C₄ and a C₈ alcohol. The secondary alcohol may also be a mixture of alcohols. As an example, the secondary alcohol may comprise a C₃ alcohol. The alcohols may contain any of branched, cyclic, or straight chains. The ZDDP may comprise the combination of about 60 mol % primary alcohol and about 40 mol % secondary alcohol. In the alternative, the ZDDP may comprise 100 mol % secondary alcohols, or 100 mol % primary alcohols.

The phosphorus-containing component of the phosphorus-containing compound may comprise any suitable phosphorus-containing component such as, but not limited to a phosphorus sulfide. Suitable phosphorus sulfides may include phosphorus pentasulfide or tetraphosphorus trisulfide.

The zinc-containing component may comprise any suitable zinc-containing component such as, but not limited to zinc oxide, zinc hydroxide, zinc carbonate, zinc propylate, zinc chloride, zinc propionate, or zinc acetate.

The reaction product may comprise a resulting mixture, component, or mixture of components. The reaction product may or may not include unreacted reactants, chemically bonded components, products, or polar bonded components.

The ZDDP or ash-containing phosphorus compound, may be present in an amount sufficient to contribute from about 0.03 wt % to about 0.15 wt % phosphorus in the lubricant composition.

In addition to, or in the alternative, an ash-free phosphorus compound may be included in a mixture of phosphorus-containing compounds. The ash-free phosphorus compound may be selected from an organic ester of phosphoric acid, phosphorous acid, or an amine salt thereof. For example, the ash-free phosphorus-containing compound may include one or more of a dihydrocarbyl phosphite, a trihydrocarbyl phosphite, a monohydrocarbyl phosphate, a dihydrocarbyl phosphate, a trihydrocarbyl phosphate, any sulfur analogs thereof, and any amine salts thereof. As a further example, the ash-free phosphorus-containing compound may include at least one or a mixture of monohydrocarbyl-and dihydrocarbyl phosphate amine salt, for example, an amyl acid phosphate salt may be a mixture of monoamylacid phosphate salt and diamylacid phosphate salt.

A weight ratio based on phosphorus from the ash-containing phosphorus compound and phosphorus from the ash-free phosphorus compound in the lubricating oil composition may range from about 3:1 to about 1:3. Another mixture of phosphorus compounds that may be used may include from about 0.5 to about 2.0 parts by weight of phosphorus from an ash-containing phosphorus compound to about 1 part weight of phosphorus from an ash-free phosphorus compound. Yet another mixture of phosphorus compounds may include about equal parts by weight of phosphorus from the ash-containing phosphorus compound and phosphorus from the ash-free phosphorus compound. Examples of mixtures of phosphorus from the ash-containing and phosphorus from the ash-free phosphorus compounds are provided in the following table.

The mixture of phosphorus-containing compounds in the lubricating oil formulation may be present in an amount sufficient to provide from about 300 to about 1200 parts per million by weight of total phosphorus in the lubricating oil formulation. As a further example, the mixture of phosphorus-containing compounds may be present in an amount sufficient to provide from about 500 to about 800 parts per million by weight of total phosphorus in the lubrication oil formulation.

The phosphorus-containing compound and titanium compound mixture disclosed herein is used in combination with other additives. The additives are typically blended into the base oil in an amount that enables that additive to provide its desired function. Representative effective amounts of the phosphorus-containing and titanium compound mixtures and additives, when used in crankcase lubricants, are listed in Table 1 below. All the values listed are stated as weight percent active ingredient.

TABLE 1 Wt. % Wt. % Component (Broad) (Typical) Dispersant 0.5–10.0  1.0–5.0 Antioxidant system 0–5.0 0.01–3.0  Metal Detergents 0.1–15.0  0.2–8.0 Corrosion Inhibitor 0–5.0   0–2.0 Metal dihydrocarbyl dithiophosphate 0.1–6.0   0.1–4.0 Ash-free amine phosphate salt 0.1–6.0   0.1–4.0 Antifoaming agent 0–5.0 0.001–0.15  Titanium Compound 0–5.0   0–2.0 Supplemental antiwear agents 0–1.0   0–0.8 Pour point depressant 0.01–5.0   0.01–1.5  Viscosity modifier 0.01–20.00  0.25–10.0 Supplemental friction modifier 0–2.0 0.1–1.0 Base oil Balance Balance Total 100 100

Dispersant Components

Dispersants contained in the DI package include, but are not limited to, an oil soluble polymeric hydrocarbon backbone having functional groups that are capable of associating with particles to be dispersed. Typically, the dispersants comprise amine, alcohol, amide, or ester polar moieties attached to the polymer backbone often via a bridging group. Dispersants may be selected from Mannich dispersants as described in U.S. Pat. Nos. 3,697,574 and 3,736,357; ashless succcinimide dispersants as described in U.S. Pat. Nos. 4,234,435 and 4,636,322; amine dispersants as described in U.S. Pat. Nos. 3,219,666, 3,565,804, and 5,633,326; Koch dispersants as described in U.S. Pat. Nos. 5,936,041, 5,643,859, and 5,627,259, and polyalkylene succinimide dispersants as described in U.S. Pat. Nos. 5,851,965; 5,853,434; and 5,792,729.

Oxidation Inhibitor Components

Oxidation inhibitors or antioxidants reduce the tendency of base stocks to deteriorate in service which deterioration can be evidenced by the products of oxidation such as sludge and varnish-like deposits that deposit on metal surfaces and by viscosity growth of the finished lubricant. Such oxidation inhibitors include hindered phenols, sulfurized hindered phenols, alkaline earth metal salts of alkylphenolthioesters having C₅ to C₁₂ alkyl side chains, sulfurized alkylphenols, metal salts of either sulfurized or nonsulfurized alkylphenols, for example calcium nonylphenol sulfide, ashless oil soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons, phosphorus esters, metal thiocarbamates, and oil soluble copper compounds as described in U.S. Pat. No. 4,867,890.

Other antioxidants that may be used in combination with the hydrocarbon soluble titanium compounds, include sterically hindered phenols and diarylamines, alkylated phenothiazines, sulfurized compounds, and ashless dialkyldithiocarbamates. Non-limiting examples of sterically hindered phenols include, but are not limited to, 2,6-di-tertiary butylphenol, 2,6 di-tertiary butyl methylphenol, 4-ethyl-2,6-di-tertiary butylphenol, 4-propyl-2,6-di-tertiary butylphenol, 4-butyl-2,6-di-tertiary butylphenol, 4-pentyl-2,6-di-tertiary butylphenol, 4-hexyl-2,6-di-tertiary butylphenol, 4-heptyl-2,6-di-tertiary butylphenol, 4-(2-ethylhexyl)-2,6-di-tertiary butylphenol, 4-octyl-2,6-di-tertiary butylphenol, 4-nonyl-2,6-di-tertiary butylphenol, 4-decyl-2,6-di-tertiary butylphenol, 4-undecyl-2,6-di-tertiary butylphenol, 4-dodecyl-2,6-di-tertiary butylphenol, methylene bridged sterically hindered phenols including but not limited to 4,4-methylenebis(6-tert-butyl-o-cresol), 4,4-methylenebis(2-tert-amyl-o-cresol), 2,2-methylenebis(4-methyl-6 tert-butylphenol, 4,4-methylene-bis(2,6-di-tert-butylphenol) and mixtures thereof as described in U.S Publication No. 2004/0266630.

Diarylamine antioxidants include, but are not limited to diarylamines having the formula:

wherein R′ and R″ each independently represents a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms. Illustrative of substituents for the aryl group include aliphatic hydrocarbon groups such as alkyl having from 1 to 30 carbon atoms, hydroxy groups, halogen radicals, carboxylic acid or ester groups, or nitro groups.

The aryl group is preferably substituted or unsubstituted phenyl or naphthyl, particularly wherein one or both of the aryl groups are substituted with at least one alkyl having from 4 to 30 carbon atoms, preferably from 4 to 18 carbon atoms, most preferably from 4 to 9 carbon atoms. It is preferred that one or both aryl groups be substituted, e.g. mono-alkylated diphenylamine, di-alkylated diphenylamine, or mixtures of mono- and di-alkylated diphenylamines.

The diarylamines may be of a structure containing more than one nitrogen atom in the molecule. Thus the diarylamine may contain at least two nitrogen atoms wherein at least one nitrogen atom has two aryl groups attached thereto, e.g. as in the case of various diamines having a secondary nitrogen atom as well as two aryls on one of the nitrogen atoms.

Examples of diarylamines that may be used include, but are not limited to: diphenylamine; various alkylated diphenylamines; 3-hydroxydiphenylamine; N-phenyl-1,2-phenylenediamine; N-phenyl-1,4-phenylenediamine; monobutyldiphenyl-amine; dibutyldiphenylamine; monooctyldiphenylamine; dioctyldiphenylamine; monononyldiphenylamine; dinonyldiphenylamine; monotetradecyldiphenylamine; ditetradecyldiphenylamine, phenyl-alpha-naphthylamine; monooctyl phenyl-alpha-naphthylamine; phenyl-beta-naphthylamine; monoheptyldiphenylamine; diheptyl-diphenylamine; p-oriented styrenated diphenylamine; mixed butyloctyldi-phenylamine; and mixed octylstyryldiphenylamine.

Another class of aminic antioxidants includes phenothiazine or alkylated phenothiazine having the chemical formula:

wherein R₁ is a linear or branched C₁ to C₂₄ alkyl, aryl, heteroalkyl or alkylaryl group and R₂ is hydrogen or a linear or branched C₁-C₂₄ alkyl, heteroalkyl, or alkylaryl group. Alkylated phenothiazine may be selected from the group consisting of monotetradecylphenothiazine, ditetradecylphenothiazine, monodecylphenothiazine, didecylphenothiazine, monononylphenothiazine, dinonylphenothiazine, monoctyl-phenothiazine, dioctylphenothiazine, monobutylphenothiazine, dibutylphenothiazine, monostyrylphenothiazine, distyrylphenothiazine, butyloctylphenothiazine, and styryloctylphenothiazine.

The sulfur containing antioxidants include, but are not limited to, sulfurized olefins that are characterized by the type of olefin used in their production and the final sulfur content of the antioxidant. High molecular weight olefins, i.e. those olefins having an average molecular weight of 168 to 351 g/mole, are preferred. Examples of olefins that may be used include alpha-olefins, isomerized alpha-olefins, branched olefins, cyclic olefins, and combinations of these.

Alpha-olefins include, but are not limited to, any C₄ to C₂₅ alpha-olefins. Alpha-olefins may be isomerized before the sulfurization reaction or during the sulfurization reaction. Structural and/or conformational isomers of the alpha olefin that contain internal double bonds and/or branching may also be used. For example, isobutylene is a branched olefin counterpart of the alpha-olefin 1-butene.

Sulfur sources that may be used in the sulfurization reaction of olefins include: elemental sulfur, sulfur monochloride, sulfur dichloride, sodium sulfide, sodium polysulfide, and mixtures of these added together or at different stages of the sulfurization process.

Unsaturated oils, because of their unsaturation, may also be sulfurized and used as an antioxidant. Examples of oils or fats that may be used include corn oil, canola oil, cottonseed oil, grapeseed oil, olive oil, palm oil, peanut oil, coconut oil, rapeseed oil, safflower seed oil, sesame seed oil, soyabean oil, sunflower seed oil, tallow, and combinations of these.

The amount of sulfurized olefin or sulfurized fatty oil delivered to the finished lubricant is based on the sulfur content of the sulfurized olefin or fatty oil and the desired level of sulfur to be delivered to the finished lubricant. For example, a sulfurized fatty oil or olefin containing 20 weight % sulfur, when added to the finished lubricant at a 1.0 weight % treat level, will deliver 2000 ppm of sulfur to the finished lubricant. A sulfurized fatty oil or olefin containing 10 weight % sulfur, when added to the finished lubricant at a 1.0 weight % treat level, will deliver 1000 ppm sulfur to the finished lubricant. It is preferred to add the sulfurized olefin or sulfurized fatty oil to deliver between 200 ppm and 2000 ppm sulfur to the finished lubricant. The foregoing aminic, phenothiazine, and sulfur containing antioxidants are described for example in U.S. Pat. No. 6,599,865.

The ashless dialkyldithiocarbamates which may be used as antioxidant additives include compounds that are soluble or dispersable in the additive package. It is also preferred that the ashless dialkyldithiocarbamate be of low volatility, preferably having a molecular weight greater than 250 daltons, most preferably having a molecular weight greater than 400 daltons. Examples of ashless dithiocarbamates that may be used include, but are not limited to, methylenebis(dialkyldithiocarbamate), ethylenebis(dialkyldithiocarbamate), isobutyl disulfide-2,2′-bis(dialkyldithiocarbamate), hydroxyalkyl substituted dialkyldithio-carbamates, dithiocarbamates prepared from unsaturated compounds, dithiocarbamates prepared from norbornylene, and dithiocarbamates prepared from epoxides, where the alkyl groups of the dialkyldithiocarbamate can preferably have from 1 to 16 carbons. Examples of dialkyldithiocarbamates that may be used are disclosed in the following patents: U.S. Pat. Nos. 5,693,598; 4,876,375; 4,927,552; 4,957,643; 4,885,365; 5,789,357; 5,686,397; 5,902,776; 2,786,866; 2,710,872; 2,384,577; 2,897,152; 3,407,222; 3,867,359; and 4,758,362.

Examples of suitable ashless dithiocarbamates are: Methylenebis-(dibutyldithiocarbamate), Ethylenebis(dibutyldithiocarbamate), Isobutyl disulfide-2,2′-bis(dibutyldithiocarbamate), Dibutyl-N,N-dibutyl-(dithiocarbamyl)succinate, 2-hydroxypropyl dibutyldithiocarbamate, Butyl(dibutyldithiocarbamyl)acetate, and S-carbomethoxy-ethyl-N,N-dibutyl dithiocarbamate. The most preferred ashless dithiocarbamate is methylenebis(dibutyldithiocarbamate).

Organomolybdenum containing compounds used as friction modifiers may also exhibit antioxidant functionality. U.S. Pat. No. 6,797,677 describes a combination of organomolybdenum compound, alkylphenothizine and alkyldiphenylamines for use in finished lubricant formulations. Examples of suitable molybdenum containing friction modifiers are described below under friction modifiers.

Friction Modifier Components

A sulfur- and phosphorus-free organomolybdenum compound that may be used as a friction modifier may be prepared by reacting a sulfur- and phosphorus-free molybdenum source with an organic compound containing amino and/or alcohol groups. Examples of sulfur- and phosphorus-free molybdenum sources include molybdenum trioxide, ammonium molybdate, sodium molybdate and potassium molybdate. The amino groups may be monoamines, diamines, or polyamines. The alcohol groups may be mono-substituted alcohols, diols or bis-alcohols, or polyalcohols. As an example, the reaction of diamines with fatty oils produces a product containing both amino and alcohol groups that can react with the sulfur- and phosphorus-free molybdenum source.

Examples of sulfur- and phosphorus-free organomolybdenum compounds include compounds described in the following patents: U.S. Pat. Nos. 4,259,195; 4,261,843; 4,164,473; 4,266,945; 4,889,647; 5,137,647; 4,692,256; 5,412,130; 6,509,303; and 6,528,463.

Molybdenum compounds prepared by reacting a fatty oil, diethanolamine, and a molybdenum source as described in U.S. Pat. No. 4,889,647 are sometimes illustrated with the following structure, where R is a fatty alkyl chain, although the exact chemical composition of these materials is not fully known and may in fact be multi-component mixtures of several organomolybdenum compounds.

Sulfur-containing organomolybdenum compounds may be used and may be prepared by a variety of methods. One method involves reacting a sulfur and phosphorus-free molybdenum source with an amino group and one or more sulfur sources. Sulfur sources can include for example, but are not limited to, carbon disulfide, hydrogen sulfide, sodium sulfide and elemental sulfur. Alternatively, the sulfur-containing molybdenum compound may be prepared by reacting a sulfur-containing molybdenum source with an amino group or thiuram group and optionally a second sulfur source. Examples of sulfur- and phosphorus-free molybdenum sources include molybdenum trioxide, ammonium molybdate, sodium molybdate, potassium molybdate, and molybdenum halides. The amino groups may be monoamines, diamines, or polyamines. As an example, the reaction of molybdenum trioxide with a secondary amine and carbon disulfide produces molybdenum dithiocarbamates. Alternatively, the reaction of (NH₄)₂Mo₃S₁₃*n(H₂O) where n varies between 0 and 2, with a tetralkylthiuram disulfide, produces a trinuclear sulfur-containing molybdenum dithiocarbamate.

Examples of sulfur-containing organomolybdenum compounds include compounds described in the following patents: U.S. Pat. Nos. 3,509,051; 3,356,702; 4,098,705; 4,178,258; 4,263,152; 4,265,773; 4,272,387; 4,285,822; 4,369,119; 4,395,343; 4,283,295; 4,362,633; 4,402,840; 4,466,901; 4,765,918; 4,966,719; 4,978,464; 4,990,271; 4,995,996; 6,232,276; 6,103,674; and 6,117,826.

Glycerides may also be used alone or in combination with other friction modifiers. Suitable glycerides include glycerides of the formula:

wherein each R is independently selected from the group consisting of H and C(O)R′ where R′ may be a saturated or an unsaturated alkyl group having from 3 to 23 carbon atoms. Examples of glycerides that may be used include glycerol monolaurate, glycerol monomyristate, glycerol monopalmitate, glycerol monostearate, and mono-glycerides derived from coconut acid, tallow acid, oleic acid, linoleic acid, and linolenic acids. Typical commercial monoglycerides contain substantial amounts of the corresponding diglycerides and triglycerides. These materials are not detrimental to the production of the molybdenum compounds, and may in fact be more active. Any ratio of mono- to di-glyceride may be used, however, it is preferred that from 30 to 70% of the available sites contain free hydroxyl groups (i.e., 30 to 70% of the total R groups of the glycerides represented by the above formula are hydrogen). A preferred glyceride is glycerol monooleate, which is generally a mixture of mono, di, and tri-glycerides derived from oleic acid, and glycerol.

Other Additives

Rust inhibitors selected from the group consisting of nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids may be used.

A small amount of a demulsifying component may be used. A preferred demulsifying component is described in EP 330,522. Such demulsifying component may be obtained by reacting an alkylene oxide with an adduct obtained by reacting a bis-epoxide with a polyhydric alcohol. The demulsifier should be used at a level not exceeding 0.1 mass % active ingredient. A treat rate of 0.001 to 0.05 mass % active ingredient is convenient.

Pour point depressants, otherwise known as lube oil flow improvers, lower the minimum temperature at which the fluid will flow or can be poured. Such additives are well known. Typical of those additives which improve the low temperature fluidity of the fluid are C₈ to C₁₈ dialkyl fumarate/vinyl acetate copolymers, polyalkylmethacrylates and the like.

Foam control can be provided by many compounds including an antifoamant of the polysiloxane type, for example, silicone oil or polydimethyl siloxane.

Seal swell agents, as described, for example, in U.S. Pat. Nos. 3,794,081 and 4,029,587, may also be used.

Viscosity modifiers (VM) function to impart high and low temperature operability to a lubricating oil. The VM used may have that sole function, or may be multifunctional.

Multifunctional viscosity modifiers that also function as dispersants are also known. Suitable viscosity modifiers are polyisobutylene, copolymers of ethylene and propylene and higher alpha-olefins, polymethacrylates, polyalkylmethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, inter polymers of styrene and acrylic esters, and partially hydrogenated copolymers of styrene/isoprene, styrene/butadiene, and isoprene/butadiene, as well as the partially hydrogenated homopolymers of butadiene and isoprene and isoprene/divinylbenzene.

Functionalized olefin copolymers that may be used include interpolymers of ethylene and propylene which are grafted with an active monomer such as maleic anhydride and then derivatized with an alcohol or amine. Other such copolymers are copolymers of ethylene and propylene which are grafted with nitrogen compounds.

Each of the foregoing additives, when used, is used at a functionally effective amount to impart the desired properties to the lubricant. Thus, for example, if an additive is a corrosion inhibitor, a functionally effective amount of this corrosion inhibitor would be an amount sufficient to impart the desired corrosion inhibition characteristics to the lubricant. Generally, the concentration of each of these additives, when used, ranges up to about 20% by weight based on the weight of the lubricating oil composition, and in one embodiment from about 0.001% to about 20% by weight, and in one embodiment about 0.01% to about 10% by weight based on the weight of the lubricating oil composition.

The hydrocarbon soluble titanium additives may be added directly to the lubricating oil composition. In one embodiment, however, they are diluted with a substantially inert, normally liquid organic diluent such as mineral oil, synthetic oil, naphtha, alkylated (e.g. C₁₀ to C₁₃ alkyl) benzene, toluene or xylene to form an additive concentrate. These concentrates usually contain from about 1% to about 100% by weight and in one embodiment about 10% to about 90% by weight of the titanium compound.

Base Oils

Base oils suitable for use in formulating the compositions, additives and concentrates described herein may be selected from any of the synthetic or natural oils or mixtures thereof. The synthetic base oils include alkyl esters of dicarboxylic acids, polyglycols and alcohols, poly-alpha-olefins, including polybutenes, alkyl benzenes, organic esters of phosphoric acids, polysilicone oils, and alkylene oxide polymers, interpolymers, copolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, and the like.

Natural base oils include animal oils and vegetable oils (e.g., castor oil, lard oil), liquid petroleum oils and hydrorefined, solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils. The base oil typically has a viscosity of about 2.5 to about 15 cSt and preferably about 2.5 to about 11 cSt at 100° C.

The following examples are given for the purpose of exemplifying aspects of the embodiments and are not intended to limit the embodiments in any way.

EXAMPLE 1 Titanium Neodecanoate

Neodecanoic acid (600 grams) was placed into a reaction vessel equipped with a condenser, Dean-stark trap, thermometer, thermocouple, and a gas inlet. Nitrogen gas was bubbled into the acid. Titanium isopropoxide (245 grams) was slowly added to the reaction vessel with vigorous stirring. The reactants were heated to 140° C. and stirred for one hour. Overheads and condensate from the reaction were collected in the trap. A subatmospheric pressure was applied to the reaction vessel and the reactants were stirred for an additional two hours until the reaction was complete. Analysis of the product indicated that the product had a kinematic viscosity of 14.3 cSt at 100° C. and a titanium content of 6.4 percent by weight.

The phosphorus retention (PR) values of comparative fluids and of fluids according to exemplary embodiments of the disclosure were determined using an Afton Catalyst Test (hereinafter “ACT”). The ACT is a fired-engine catalyst-aging test developed by Afton Chemical Corporation to assess volatility-related lubricant effects on catalyst deactivation. The ACT uses a 2001MY Ford 4.6 L SOHC V8 engine connected to an eddy-current dynamometer and is operated for 240 hours. Test operating conditions are selected to be consistent with approximately 50,000 km of steady-state highway cruising with the exception of exhaust gas, engine oil, and engine coolant operating temperatures. To minimize the effects of thermally-related catalyst deactivation, the engine exhaust gas temperature is held well below the 750° C. level where this effect is known to occur. To maximize the effects of oil and oil chemistry volatility on catalyst deactivation, engine oil and coolant temperatures are controlled to the highest practical levels, namely, 145° C. and 122° C., respectively. Oil consumption is accurately determined by performing a mass balance on the amount removed versus the amount installed in the engine. The operating conditions of the ACT are listed in Table 2.

TABLE 2 Operating Conditions of Afton Catalyst Test Test Engine: Ford SOHC 4.6 L V8 operated on un- leaded gasoline Test Fuel: EEE Emissions-grade gasoline Test Catalyst: Ford Part Number 3W1Z-5E212-GB Test Duration: 240 hours Oil Change Interval: 24 hours Oil Charge: 4500 grams Engine Speed: 2000 rpm Oil Temperature: 145° C. Coolant Temperature: 122° C. Catalyst Inlet Temperature: 550° C. Fuel Consumption: 10.7 kg/hr

With each oil change during the test, a sample of oil is taken for analytical purposes. The elemental concentration and viscosity properties are determined through the use of an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) and kinematic viscometers. The oil consumption and elemental concentration data provide the amount of oil consumed through volatile means relative to the amount consumed through bulk oil changes. The data also enable the calculation of the amount of phosphorus throughput and percent phosphorus retention.

As the oil ages in an engine, a part of the base stock evaporates or distills, leaving behind the additive elements. The percent of calcium concentration increase is directly proportional to the percent loss of base stock through volatile means. Phosphorus also concentrates in the used oil, but to a lesser degree, due to the tendency of certain phosphorus species from the ZDDP to volatilize at elevated temperatures. Phosphorus retention (PR) in the used oil is calculated by multiplying a ratio of the change in calcium concentration (New oil/Used oil) with the ratio of the change in phosphorus concentration (Used oil/New oil) as shown by the equation:

PR=(Ca New oil/Ca Used oil)×(P Used oil/P New oil)×100.

Calcium is used in the calculation of phosphorus retention to determine the increase in phosphorus concentration due to base oil volatility, since calcium, is not volatile in the lubricant composition.

Catalyst performance may be determined before and after the 240-hour aging process by the performance of a Conversion Efficiency (CE) test. In the CE evaluation the engine is operated at a steady-state condition while the exhaust gas temperature is controlled to maintain a steady catalyst inlet temperature. Exhaust inlet temperature is stepped up in 15° C. intervals from 200° C. to 440° C. while hydrocarbon (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) emissions are measured through probes inserted before and after the catalyst. Curves may be constructed from the data to provide the “T50” value or temperature where 50% conversion occurs for each emission type. By comparing the T50 values before and after aging the relative amount of catalyst degradation may be determined and compared to aged oils. The 240 hour oil aging process typically results in an increase in all of the T50 values, except when the oil contains no phosphorus-containing additives.

EXAMPLE 2

A 100,000-mile New York Taxi field test was conducted on a conventional lubricant formulation and a lubricant formulation containing an amount of titanium neodecanoate sufficient to provide 500 ppm titanium metal to the lubricant composition. The results and statistical comparison are shown in Table 3. All vehicles started the test with new engines and had 5000 or 10,000-mile oil change intervals. Four vehicles were operated on a lubricant composition containing 500-ppm Ti; three vehicles were operated on the same lubricant formulation without titanium.

TABLE 3 Field Test for Phosphorus Retention (PR) No. of Phos. Ret. Oil Composition Vehicle ID tests (%) Std. Dev. No titanium 12B 19 88.1 5.8 No titanium 14A 19 86.4 4.4 No titanium  1A 20 87.7 4.8 500 ppm titanium 24A 19 92.2 5.4 500 ppm titanium 57A 20 91.6 4.6 500 ppm titanium 60B 19 93.3 4.6 500 ppm titanium  7A 19 91.7 5.2

Consistent with Sequence IIIG testing, the vehicles run on lubricants containing the titanium-containing compound averaged higher phosphorus retention at 92.2% PR versus 87.4 PR for the baseline provided by the vehicles run on lubricants devoid of titanium.

EXAMPLE 4

A design of experiments (DOE) was performed on fully-formulated oils containing various concentrations of titanium from titanium neodecanoate (TND). The formulations and components are shown in Table 4. Another variables included in this DOE was the phosphorus level. In total, fifteen separate blends were evaluated in the Sequence IIIG engine test—a test that operates 100 hours at 150° C. oil temperature. As part of the IIIG test, 20-hour interval oil samples are taken and analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to determine the changes in elemental concentrations that result from aging. The data were used to calculate Phosphorus Retention percent after 20 hours of aging (PR, %) according to the above formula.

TABLE 4 Sequence IIIG Design of Experiment Formulation Data and Phosphorus Retention Results Phosphorus ZDDP Titanium Retention Run No. (wt. %) (ppm) (%) 1 0.58 106 82.2 2 0.58 53 84.6 3 0.93 106 84.1 4 0.93 53 78.6 5 0.93 106 83.0 6 0.58 53 83.2 7 0.58 53 83.5 8 0.58 106 85.2 9 0.58 106 90.2 10 0.79 80 85.6 11 0.93 53 87.0 12 0.93 106 82.2 13 0.93 106 82.8 14 0.93 106 81.0 15 0.93 106 82.1

A linear regression statistical analysis of the DOE data concluded that increasing titanium concentration has a significant positive effect improving PR, %. Oils containing 100 ppm titanium from TND, on the average, exhibited an improvement of 4.25 PR, % (p-value of 0.008).

At numerous places throughout this specification, reference has been made to a number of U.S. Patents. All such cited documents are expressly incorporated in full into this disclosure as if fully set forth herein.

The foregoing embodiments are susceptible to considerable variation in its practice. Accordingly, the embodiments are not intended to be limited to the specific exemplifications set forth hereinabove. Rather, the foregoing embodiments are within the spirit and scope of the appended claims, including the equivalents thereof available as a matter of law.

The patentees do not intend to dedicate any disclosed embodiments to the public, and to the extent any disclosed modifications or alterations may not literally fall within the scope of the claims, they are considered to be part hereof under the doctrine of equivalents. 

1. A lubricated surface comprising a lubricant composition containing a base oil of lubricating viscosity, at least one phosphorus-containing compound, and an amount of at least one hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.
 2. The lubricated surface of claim 1, wherein the lubricated surface comprises an engine drive train.
 3. The lubricated surface of claim 1, wherein the lubricated surface comprises an internal surface or component of an internal combustion engine.
 4. The lubricated surface of claim 1, wherein the lubricated surface comprises an internal surface or component of a compression ignition engine.
 5. The lubricated surface of claim 1, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 50 to about 1000 ppm in the lubricant composition.
 6. The lubricated surface of claim 1, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 100 to about 500 ppm in the lubricant composition.
 7. The lubricated surface of claim 1, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 50 to about 300 ppm in the lubricant composition.
 8. The lubricated surface of claim 1, wherein the hydrocarbon soluble titanium compound comprises titanium neodecanoate.
 9. A motor vehicle comprising the lubricated surface of claim
 1. 10. The vehicle of claim 9, wherein the amount of hydrocarbon soluble titanium compound provides from about 1 to about 1000 parts per million titanium in the lubricant.
 11. A vehicle having moving parts and containing a lubricant for lubricating the moving parts, the lubricant comprising an oil of lubricating viscosity, at least one phosphorus-containing compound, and an amount of at least one hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.
 12. The vehicle of claim 11, wherein the hydrocarbon soluble titanium compound comprises titanium neodecanoate.
 13. The vehicle of claim 11, wherein the moving parts comprise a heavy duty diesel engine.
 14. The vehicle of claim 11, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 50 to about 1000 ppm in the lubricant composition.
 15. The vehicle of claim 11, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 100 to about 500 ppm in the lubricant composition.
 16. The vehicle of claim 11, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 50 to about 300 ppm in the lubricant composition.
 17. A fully formulated lubricant composition comprising a base oil component of lubricating viscosity, at least one phosphorus-containing compound, and an amount of hydrocarbon soluble titanium-containing agent effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium-containing agent, wherein the titanium-containing agent is essentially devoid of sulfur and phosphorus atoms.
 18. The lubricant composition of claim 17, wherein the lubricant composition comprises a low ash, low sulfur, and low phosphorus lubricant composition suitable for compression ignition engines.
 19. The lubricant composition of claim 17, wherein the hydrocarbon soluble titanium-containing agent comprises titanium neodecanoate.
 20. The lubricant composition of claim 17, wherein the amount of hydrocarbon soluble titanium-containing agent provides from about 50 to about 1000 parts per million titanium in the lubricant composition.
 21. The lubricant composition of claim 17, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 100 to about 500 ppm in the lubricant composition.
 22. The lubricant composition of claim 17, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 50 to about 300 ppm in the lubricant composition.
 23. A method of increasing phosphorus retention in engine lubricant compositions during operation of an engine, wherein the phosphorus retention is sufficient to reduce catalyst poisoning, comprising contacting the engine parts with a lubricant composition comprising a base oil of lubricating viscosity, at least one phosphorus-containing compound, and an amount of a hydrocarbon soluble titanium compound effective to provide an increase in phosphorus retention of the lubricant composition greater than an increase in phosphorus retention of the lubricant composition devoid of the hydrocarbon soluble titanium compound.
 24. The method of claim 23, wherein the engine comprises a heavy duty diesel engine.
 25. The method of claim 23, wherein 19, wherein the hydrocarbon soluble titanium-containing agent comprises titanium neodecanoate.
 26. The method of claim 23, wherein the amount of hydrocarbon soluble titanium-containing agent provides from about 50 to about 1000 parts per million titanium in the lubricant composition.
 27. The method of claim 23, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 100 to about 500 ppm in the lubricant composition.
 28. The method of claim 23, wherein the amount of hydrocarbon soluble titanium compound provides an amount of titanium ranging from about 50 to about 300 ppm in the lubricant composition. 